Topic: Eten and alkenes - hydrocarbons with multiple bonds between carbon atoms

Target group

Student of an eight‑year elementary school

Core curriculum

Elementary school. Chemistry.

VIII. Compounds of carbon with hydrogen - hydrocarbons. The student:

5) creates general formulas of homologous series of alkenes and alkynes (based on the formulas of subsequent alkenes and alkynes); writes the total formula of the alkene and alkyne with the specified number of carbon atoms; forms the names of alkenes and alkynes based on the names of the corresponding alkanes; draws structural and semi‑structural (group) formulas of alkenes and alkynes with straight‑chain atoms up to five carbon atoms.

General aim of education

The student acquires knowledge and skills about the topics discussed in the classes

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• what are the terms: alkenes , unsaturated hydrocarbons

• to draw structural and semi‑structural formulas of alkenes and alkynes;

• to write general formulas of homologous alkenes and alkynes.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

Realization

1. The teacher, referring to the concept of saturated hydrocarbons, asks students to explain it. Supplements statements and provides information about unsaturated hydrocarbons and alkenes.

2. The teacher explains the rules for naming the alkenes and writes the rule on the board. Then he asks willing/selected students to give names of compounds to 10 carbon atoms in the molecule. Other students verify the answers of colleagues.

3. The teacher presents a film from the abstract „Research on the insatiable nature of ethene”. Before this happens, he instructs students to formulate and record research questions and hypotheses in the observation diary. Observations, conclusions and a summary of the experiment viewed should also be recorded in the journals.

4. The teacher asks students to analyze the model of the ethene molecule and then draw the propene model (task 1).

5. Individual work. Students perform an interactive exercise on naming and aklen formulas. Together with the teacher, they discuss the answers.

6. At the end of this part of the class, the teacher divides the class into groups and writes on the table the summary formulas of several alkenes (from 5 to 10 carbon atoms per molecule). Teacher informs that the task of each group will be to give the name and draw the structural formula of the selected compound. The group that will present the right solution wins first.

Summary

1. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

2. Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Eten and alkenes - hydrocarbons with multiple bonds between carbon atoms

While working on the oil composition, chemists – apart from saturated hydrocarbons – separated a different group of organic compounds, alkenes. Alkenes are hydrocarbons in which molecules between carbon atoms have one double bond (multiple). The remaining bonds are single.

Hydrocarbons with at least one multiple bond (double or triple), are called unsaturated.

Unsaturated hydrocarbons, like saturated ones (alkanes), form a homologous series. The name of alkene is formed from the name of an alkane with the same number of carbon atoms in the molecule, adding the ending - ene instead of - ane. The table contains alkenes arranged according to the increasing number of carbon atoms – a homologous series of alkenes.

All alkene molecules in the homologous series have twice more hydrogen atoms than carbon atoms. Thus, the general formula of alkenes is:

${\text{C}}_n{\text{H}}_{2n}$

$\text{n}$ ≥ 2 number of carbon atoms in the molecule.

The simplest representative of alkenes is ethene, a compound commonly known as ethylene. Its molecule is composed of two carbon atoms and four hydrogen atoms.

Based on the location of the carbon in the periodic table, we predict that its atom has four valence electrons. Therefore, it is always tetravalent in organic compounds – it can create up to four bonds. In the ethene molecule, the carbon atoms are connected to each other by a double bond (multiple bond). Each of the carbon atoms is connected to two hydrogen atoms.

• Unsaturated hydrocarbons are hydrocarbons in which molecules between carbon atoms in addition to single bonds there is one double bond (alkenes), and hydrocarbons in which molecules between carbon atoms have one triple bond (alkynes).

• Alkenes form a homologous series with the general formula of ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.

• In the ethene molecule, the carbon atoms are connected to each other by a double bond (multiple). Each of the carbon atoms is linked to two hydrogen atoms.

• In unsaturated hydrocarbon molecules, multiple bonds can be located between different carbon atoms. This phenomenon is called position isomerism.